1. Field of the Invention
The present invention relates to a sewn cover assembly having a foam layer integral therewith, which is formed by sewing plural separate cover materials together and subjecting them to foaming to create a foam layer integrally therewith, and also to a product which is formed by foaming process integrally with such sewn cover assembly to create a foam cushion member within the sewn cover assembly.
2. Description of Prior Art
What is known as a trim cover assembly is normally formed from a surface cover layer and foamed padding layer in an integral fashion and used to cover a vehicle or automotive seat and associated parts thereof, such as a headrest or armrest. In particular, the headrest or armrest is formed, using a closed three-dimensional trim cover assembly and subjecting it to a foaming process. According to ordinary process for forming the headrest or armrest, plural separate cover sections are sewn together by a sewing machine to form a three-dimensional body of trim cover assembly and then a liquid foaming material is injected and cured in the hollow inside of the so sewn trim cover assembly to create a foamed cushion member therewithin.
The problem inherit in this process is a high likelihood of the liquid foaming material being leaked from the sewn jointed points of trim cover assembly where plural cover materials are sewn together to form the trim cover assembly, or strictly stated, through the needle holes formed by sewing machine needle in the jointed seam areas of trim cover assembly.
To avoid such leakage problem, various ways have been done and proposed. For example, the Japanese Laid-Open Patent Publication No. 8-309765 suggests an overlock sewing method by which both extreme ends of two covering members are juxtaposed with each other and sewn together in an overlock manner, using the combination of thin and thick threads, to forcibly close each needle hole in an attempt to prevent leakage of a liquid foaming material therethrough. Further, the Japanese Laid-Open Patent Publication No. 8-243271 suggests to use an elastic piece and sewing it to and along a sewn line or seam at which two covering members are sewn together so that the elastic piece serves to fill the needle holes in the seam.
However, those hitherto techniques have been found defective in expensive, troublesome sewing processes requiring a particular sewing machine like overlock machine and plural different threads in the case of the former (8-309765) and requiring additional step of sewing a leakage preventive material to the seam of sewn trim cover assembly in the case of the latter (8-243271).
In view of the above-stated drawbacks, it is a primary purpose of the present invention to provide a sewn cover assembly which is easy to form and completely prevents leakage of liquid foaming material through needle holes formed therein.
To achieve such purpose, a sewn cover assembly of the present invention is basically comprised of:
plural cover elements, each being preformed in a predetermined shape;
said plural cover elements being sewn together by a sewing machine, using a first thread and a second thread, into a predetermined configuration of the sewn cover assembly, wherein said first thread is of an elastic and flexible property and is large in thickness relative to said second thread.
Accordingly, the first thread is partly collapsed resiliently points by the second thread and further forcibly inserted into needle holes formed in the juxtaposed cover elements together with the second thread. Thus, such forcible insertion of both two threads in the needle hole completely closes and seals the needle hole itself against leakage of a liquid foaming material through the needle holes during a foaming process wherein the liquid foaming material is injected and cured in the predetermined configuration of sewn cover assembly.
Preferably, the first thread may be 5 to 20 times as thick as the second thread.
One preferred mode of the first thread may be a simple thread of such large thickness, such as a woolen yarn, or alternatively, another preferred mode the same be a twisted thread which is formed by spinning and twisting a long tape of elastic material, such as a long tape of wooly nylon or non-woven fabric material.
It is another purpose of the present invention to provide a product foamed integrally with the above-described sewn cover assembly.
For that purpose, a liquid foaming material is injected and cured in the sewn cover assembly to create a foam cushion member therein in an integral manner, so that a resulting product is obtained without any leakage of the liquid foaming material through the needle holes in the cover assembly. The resulting product may be used in any desired forms. For example, in the case where the predetermined configuration of sewn cover assembly is a box-like three-dimensional trim cover assembly for headrest, the resulting product may comprise a headrest for use on an automotive seat, the headrest being formed such that a headrest frame is placed in the box-like three-dimensional trim cover assembly and provided therein integrally with the foam cushion member. In the case where the predetermined configuration of sewn cover assembly is a box-like three-dimensional trim cover assembly for armrest, the resulting product may comprise an armrest for use with an automotive seat, the armrest being formed such that an armrest frame is placed in the box-like three-dimensional trim cover assembly and provided integrally with said foam cushion member.
In one aspect of the present invention, because of the above-discussed complete filling of needle hoes effected by insertion of thick thread, it is optionally possible that at least one of the plural cover elements may be of one layer structure comprising only one surface cover member while another of the plural cover elements may be of at least two-layer lamination structure comprising a surface cover layer and a foam padding layer integral therewith.
Other various features and advantages of the present invention will become apparent from reading of the descriptions hereinafter with reference to the annexed drawings